It has heretofore been proposed to employ electro-optical techniques for detecting commercial variations in containers of glass or plastic composition. The term "commercial variations" refers to variations from nominal design that may affect the commercial acceptability of the containers. Commercial variations may include, for example, variations in color or dimension from those desired by the manufacturer or customer, surface variations especially around the sealing surface of the container, or manufacturing anomalies in the container sidewall such as stress cracks or inclusions.
U.S. Pat. No. 4,874,940 discloses a method and apparatus for electro-optical inspection of containers as the containers are transported along a linear conveyor. The apparatus includes an arm that is angulated over the conveyor for engaging and laterally diverting containers as the containers are brought by the conveyor into abutment with the arm. (Directional adjectives such as "lateral" and "longitudinal" are taken with respect to the direction of linear conveyor motion, unless otherwise indicated.) The diverted containers are brought into engagement with a drive belt, which is spaced laterally from the conveyor and cooperates with a parallel section of the arm to propel the containers longitudinally over a wear plate while rotating each container about its central axis. A light source positioned beneath the wear plate directs a linear light beam through a slot in the wear plate, and through the containers as they are rotated and transported along the wear plate, onto a camera disposed above the wear plate. The camera is coupled to suitable electronics for detecting commercial variations in the containers as a function of the light energy incident on the camera. Following transport along the wear plate slot, the containers are brought into engagement with a second drive belt that is angulated with respect to the longitudinal direction of the conveyor so as to divert the containers in sequence back onto the conveyor.
Although the method and apparatus disclosed in the noted patent address problems theretofore extant in the art, further improvements remain desirable. In particular, it is an object of the present invention to provide a method and apparatus for in-line inspection of containers, of the general type disclosed in the noted patent, that reduce instability of the containers at the infeed and/or outfeed ends of the apparatus, which might otherwise lead to hesitation, stumbling and toppling of the containers, which in turn would require manual intervention by an operator to restore the inspection station to proper operation. Another object of the present invention is to provide a method and apparatus of the described character that are characterized by ease of container removal in the event of jamming or for other reasons, and that terminate operation of the inspection station in the event of a container jam. Yet another object of the invention is to provide a method and apparatus of the described character that are characterized by reduced maintenance requirements and increased operating lifetime. A further object of the invention is provide to a method and apparatus of the described character that can be readily adapted for use in conjunction with large containers--i.e., containers such as jars that have a large diameter compared with axial length. Yet another object of the present invention is to provide a method and apparatus of the described character that are characterized by ease of adjustment, and that can be adjusted during operation. Another object of the present invention is to provide a method and apparatus that achieve one or more of the foregoing objectives, and can be readily retrofitted into existing inspection installations in place of the apparatus disclosed in the noted patent.